Ernesto Diaz
From: Poland
Location: Kraków
On Useme since 12 October 2026
About me
Senior full-stack developer: React, TypeScript, Node/NestJS, PHP/Laravel, PostgreSQL, WooCommerce plugins. By day I work on large production systems; on Useme I take well-defined jobs:
- API integrations and webhooks (shop, ERP, CRM, payments, carriers), - automations (n8n, Make, custom scripts) and small web apps, - fixes and features in existing Node/React/PHP codebases, - diagnosis when something is broken and nobody knows why.
How I work: fixed price and deadline agreed before I start, scope written down in the chat, every change tested and explained step by step. I build with AI (Claude Code), so delivery is fast, but I am accountable for the result, not for generated code.
Registered business in Poland, VAT invoice. Author of InvoDev (KSeF invoicing for tradespeople) and of Frontfabryka Listing Check for WooCommerce, a plugin tested on 1,288 real products.
Categories
CV / Résumé
Nov 2022 - Now
Senior Frontend Engineer / Consultant
IT consultancy, Kraków (enterprise clients)
Enterprise React/TypeScript for four international clients: industrial cost-modelling platforms with nested validation rules, a mobile device management product (thousands of devices), and a 20-component library adopted across 5+ internal tools.
Jan 2019 - Oct 2022
Frontend Developer
Grand Parade / William Hill
React account features for high-traffic gambling and casino products: KYC, responsible-gambling controls and account settings, in a regulated real-money environment. A/B tests, stability work, reviews, documentation, onboarding a new developer.
Jan 2017 - Dec 2018
Web Developer
Freelance (w3bsolutions.com)
Delivered and optimised small-business websites, working directly with clients on requirements and technical guidance. JavaScript, HTML5, CSS3.
Jan 2012 - Dec 2016
Web Developer and Database Manager
DESOFT S.A.
JavaScript/HTML/CSS modules for ERP applications and maintenance of the PostgreSQL database structures behind them.
Portfolio
My own product: invoicing for tradespeople and small businesses, built on site from a phone. Polish KSeF e-invoices (FA(3)), offline mode with sync, job photos, NIP/REGON validation. Next.js, Node, PostgreSQL. Designed, built and deployed by me.
Frontfabryka Listing Check for WooCommerce
Free WordPress plugin that scans a WooCommerce catalog against InPost Von Halsky listing rules: EAN check digit, description length, images, brand, price, GPSR safety data. Per-variant checks, filters, CSV export, PL/EN. Tested on 1,288 products.